1. Field of the Invention
The present invention relates to a rotary press having a printing unit for printing picture on a web fed by a paper feeder.
2. Description of Related Art
As shown in FIG. 4, a general offset rotary press 1 has a paper feeder 2 for feeding consecutive web W, a delivery device 3 for delivering the web W from the paper feeder 2 to downstream (in right direction in the figure), a printer 5 including a plurality of printing unit 5A to 5D having blanket cylinder 4 etc. thereinside for printing picture on the web W delivered by the delivery device 3, a drier 6 for drying ink distributed on the printed web W, a cooler 7 for cooling the web W sent from the drier 6, and a folding machine 8 for cutting and folding the web W.
As shown in FIG. 5, the respective printing units 5A to 5D (represented by the printing unit 5A hereinafter) of the rotary press 1 include a print cylinder 50 having printing form, the blanket cylinder 4 for printing on the web W by being transferred with ink from the print cylinder 50, a ink furnishing unit 51 for feeding the ink to the print cylinder 50, and a water feeder 61 for feeding water to the print cylinder 50.
Incidentally, the print cylinder 50, the ink finishing unit 51 and the water feeder 61 are provided on the printing unit 5A to upper and lower side of the web W for double-side printing of the web W.
The ink furnishing unit 51 includes an ink fountain 52 for storing the ink, an ink fountain roller 53 for drawing the ink out from the ink fountain 52, an ink key (not shown) for adjusting ink draw amount by the ink fountain roller 53, and an ink ductor 55 for transferring the ink from the ink fountain roller 53 to downstream ink transferring rollers 54.
The ink transferring rollers 54 include a plurality of ink distributing roller 56, a plurality of ink smoothing roller 58 and a plurality of ink form roller 59. The ink drawn out by the ink fountain roller 53 is kneaded and leveled while passing the rollers 54 and is fed to the print cylinder 50.
The water feeder 61 includes a water fountain 62, a water fountain roller 63 for drawing water out from the water fountain 62, a dampening roller 64 for transferring the water from the water fountain roller 63, a water form roller 65 for applying the water to the print cylinder 50, and a water rider 66, the dampening roller 64, the form roller 65 and the rider 66 forming the water transferring rollers 67. The water drawn out by the water fountain roller 63 is leveled while passing the water transferring rollers 67 and is fed to the print cylinder 50.
The drive of the ink transferring rollers 54 and the water transferring rollers 67 is conventionally transmitted from a main motor to respective printing units 5A to 5D through a line shaft. The drive is transmitted to printing cylinders such as the print cylinder 50 by a bevel gear etc., wherefrom the drive is transmitted to the ink transferring rollers 54 and the water transferring rollers 67 through a clutch 70 and an idler gear 71, and further through a gear cooperative mechanism 72 as shown in a driving system of FIG. 6.
When the ink transferring rollers 54 are driven, the drive from the clutch 70 and the idler gear 71 is transmitted to a gear 73A coaxial with one of the three ink smoothing rollers 58. A gear 74 is meshed with the gear 73A and a timing pulley 75 is provided coaxially with the gear 74. When a rotation of the gear 73A is transmitted to the gear 74 and the other three gears 73, the four ink smoothing rollers 58 are rotated and the ink transferring rollers 54 such as the ink distributing roller 56 are dragged to be rotated as shown in FIG. 5.
The gear cooperative mechanism 72 is composed including the gear 73A, 73, 74 and the timing pulley 75. The ink fountain roller 53 is driven by an ink fountain roller driving motor (not shown).
When the water transferring rollers 67 are driven, the form roller 65 is rotated by meshing the clutch 70 and a water driving gear 77 coaxial with the water form roller 65 and the water rider 66 is dragged to be rotated by the rotation.
Incidentally, the water fountain roller 63 is driven by a driving motor (not shown).
However, following disadvantages occur in driving the ink transferring rollers and the water transferring rollers of the conventional rotary press.
First, since the ink transferring rollers 54 and the water transferring rollers 67 are driven by the line shaft driven by a main motor and the gear cooperative mechanism connected to the line shaft, the ink transferring rollers 54 and the water transferring rollers 67 are driven at a rate proportional to a peripheral speed of the print cylinder. In order to change the peripheral speed of the respective rollers 54 and 67, the number of teeth of the gear has to be changed or roller diameter has to be changed, which is difficult. Accordingly, doubling and hickey, which can be prevented by changing the peripheral speed, are likely to be caused, thereby preventing the print quality from being improved.
Second, since the ink transferring rollers 54 and the water transferring rollers 67 are driven by the gear cooperative mechanism connected to the line shaft, the respective rollers 54 and 67 cannot be independently driven and suspended without driving or suspending the printer body. Accordingly, an ink film is not formed on the ink transferring rollers 54 and emulsified status is not generated on the water transferring rollers 67 in advance and such process has to be conducted in initiating printing process. Therefore, extra web W is used before generating the ink film and the emulsified status, which increases paper spoilage.
Third, since the drive is transmitted and shut between; the ink transferring rollers 54 and the water transferring rollers 67; and the printer body side by switching the clutch, both rollers 54 and 67 cannot be separately driven. Accordingly, when both of the rollers 54 and 67 or either one of the rollers has to be run idle for maintenance etc., the printer body has to be actuated. In this case, since the web W sandwiched between the blanket cylinders 4 will be fed, extra portion of the web W has to be cut. Consequently, the web W has to be inserted between the blanket cylinders, which is troublesome and deteriorates efficiency of printing process since the clutch has to be set on and off to deteriorate operability.
Fourth, the peripheral speeds of the print cylinder and the water form roller preferably have a difference in order to remove the hickey as the printing failure. On the other hand, in printing on a rough paper etc., paper dust or the like may be raised when there is a peripheral speed difference and the paper dust is likely to adhere on the surface of the water form roller, thereby hindering printing with good quality. However, since the water transferring rollers 67 cannot be driven with variable speed in the conventional drive, the peripheral speed of the water rollers cannot be changed freely in accordance with the paper. Accordingly, it is difficult to print on printing papers having different paper quality (e.g. coated paper and rough paper), thereby hindering improvement of printing quality.
The above problems occur because the rollers are mechanically driven. Accordingly, an electrically controlled driving means 88 can be designed as shown in FIG. 7.
In this arrangement, when the individual member (such as first roller and ink form roller) is independently speed-proportionally-operated in proportion to a predetermined standard (spindle rotation), speed of the standard is detected by a rotational frequency detecting device 80 and spindle rotational frequency is outputted to an electric motor controller 81 by a ratio setting device 82 as a speed command defined in proportion to the first axis rotation speed. The electric motor controller 81 compares and operates the speed command from the ratio setting device 82 by a processor 85 and a speed sensor 84 for detecting speed of the motor 83. After adding or subtracting the difference, the command is outputted to a speed controller 86 and the motor 83 is driven by a command from the speed controller 86 through an amplifier 87.
In the above arrangement, however, control accuracy is difficult to be obtained because of being general-type proportional operation method, so that speed fluctuation unevenness is likely to be caused on account of touch shock of the ink fountain roller and a shock by a gap of the print cylinder, thereby being difficult to keep the peripheral speed relative to the print cylinder surface. Accordingly, water pattern and ink pattern are likely to be generated on the printing paper, thereby deteriorating print quality.
Further, in order to exclude such rotational speed unevenness, inertia on the motor side and output torque have to be made larger for enduring momentary torque fluctuation, which requires large-capacity motor, thereby obstructing reduction of size of the unit and cost.